A high-frequency response relaxed eddy accumulation flux measurement system for sampling short-lived biogenic volatile organic compounds

A second‐generation relaxed eddy accumulation system was built and tested with the capability to measure vertical biogenic volatile organic compound (VOC) fluxes at levels as low as 10 µg C m−2 hr−1. The system features a continuous, integrated gas‐phase ozone removal procedure to allow for the measurement of highly reactive species such as β‐caryophyllene and polar terpenoids such as linalool. A two‐component internal standard continuously added to the accumulators was used to correct for switching‐induced volumetric errors and as a check on VOC losses exceeding accumulator tube adsorption limits. In addition, the internal standards were used to demonstrate that accumulators quickly return to target flow rates at segregation valve switching frequencies up to at least 0.8 Hz. The system was able to measure daytime hourly fluxes of individual biogenic VOC including oxygenated terpenoids, monoterpenes, and sesquiterpenes. Key Points Flux measurement methodology for high reactivity, semi‐volatile VOCs REA with integrated gas phase ozone removal Internal standard used for volumetric corrections and accumulator VOC breakthrough